The present invention relates generally to an alarm system for use in an automotive vehicle for giving an alarm when drowsiness of a driver is detected, to prevent the driver from dozing at the wheel. More particularly, the invention relates to an alarm system which detects drowsiness of the driver on a basis of abnormal steering operation.
Vehicle drivers are apt to feel drowsy during relatively high speed cruising such as cruising on a highway. The drowsy driver may make abnormal steering operations which, otherwise, will not be made in normal driving condition. There are some typical abnormal steering operations which the drowsy driver is apt to make. Therefore, if such abnormal steering operations can be detected based on a vehicle operating condition, an alarm can be given to the driver to prevent the driver from dozing at the wheel.
Drowsiness of the driver or falling asleep of the driver can be detected by detecting variation of certain parameters into an abnormal range. For example, since the steering angle variable is unnecessarily increased when the driver feels drowsy or falls asleep, drowsiness of the driver can be detected by detecting a steering angle variation in steering which is larger than the steering angle variations in normal driving conditions. On the other hand, even if the steering angle variable exceeds the normal range, it should still be considered as a normal driving condition if the vehicle transmission is frequently shifted. Further, since the normal steering angle range is inversely proportional to the vehicle speed, i.e., the range of the normal steering angle will become smaller as the vehicle speed increases, the vehicle speed or other parameter representative of vehicle speed higher than a predetermined vehicle speed will be considered as one of parameter to detect drowsiness of the driver.